This invention relates to a device having a function of automatically adjusting a voltage which is output as an output voltage at a voltage within a predetermined range even when an input voltage is increased or decreased beyond the predetermined range of the voltage in an electric power saving device, such as a transformer.
In a conventional economy electricity apparatus, as shown in FIG. 3, plural sets of exciting coils L3, L4, L7 and L8, which are wound on a single-phase core-type core (9) in a mutually connected series, are connected between the ends of plural sets of main coils L1, L2, L5 and L6 which are phase-wound on the single- phase core-type core (9), in which the combinations of the exciting coils L3, L4, L7 and L8 are controlled by thyristors (1, 2) connected with a voltage sensor provided at the input ends of the main coils L1 and L5, whereby an input voltage is prevented from unnecessarily dropping.
For example, a circuit, on which the exciting coils are combined to cause the voltage to output by dropping by 6 V for the input voltage 100 V, is automatically changed to another circuit which has a lower-voltage rate of 3 V at a predetermined input voltage value, therefore, when the input voltage is decreased, the voltage is prevented from unnecessarily dropping so as to hold down the effect on a load as much as possible.
However, in order not to decrease the input voltage unnecessarily, in the conventional economy electricity apparatus, the output voltage value is adjusted by controlling only the value the input voltage is dropped, so that, when the value of the input voltage is smaller than the minimum voltage value required for a load, the voltage is therefore further decreased unnecessarily, consequently affecting the load.